Hair turns gray when pigment production stops.
It is stem cells that produce the pigment and they begin to die around the age of 25 in men and about five years later in women.
Premature graying is largely hereditary.
The road to gray hair
1. Stem cells in the upper layers of the skin develop into pigment-producing pigment cells. They move down to the bottom of the hair follicle.
2. The pigment cells produce pigments that give the hair its characteristic color. The cells deposit the pigment in the hair shaft.
3. With age, these pigment cells begin to die and when there are no more pigment cells to give the hair color, it turns gray.
4. Each hair follicle develops in its own way. Nose hair often turns gray first, then head hair, beard, body hair and eyebrows last.
